<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<p id="demo">单击按钮显示修改年份后的日期。</p>
<button onclick="myFunction()">点我</button>
<script>
function myFunction(){
	var d = new Date();
	d.setFullYear(1999,6,31);
	var x = document.getElementById("demo");
	x.innerHTML=d;
}
</script>

</body>
</html>
